This invention relates to a computer system suitable for effecting a sequence control and a servo-control.
In the prior art, a sequence control and a servo-control have been effected by a programmable controller (PC) or a computerized numerical controller (CNC). However, these control systems involve certain problems at the time of programming. For example, in the case of the PC, since programs are prepared with ladder circuits, there is a large defect that the programs cannot be prepared in the same manner as in a general purpose computer. More particularly, when a program is prepared using ladder circuits, it is difficult to prepare a program for a circuit such as a sequence circuit wherein the result differs depending upon the past or preceding state of the circuit. Even if such a program could be prepared, preparation of such a complicated program is much more difficult. In addition, assisting means for preparing a program that is used as a means for automatically preparing a portion of the program and programming technique is much inferior to that of the high grade general purpose computer so that such means and technique used in the general purpose computer cannot be used for the PC.
Since the control speed of the PC is limited by the cycle time thereof, a high response speed of less than several milliseconds cannot be obtained. Moreover, as the number of input/output ports of the PC is also limited, in many cases inputting and outputting of numerical data become impossible. Furthermore, with the PC it is difficult to judge conditions including an arithmetic computation. As a result, it has been difficult to directly control a sequence system and a servo-system by using a PC.
In the case of a CNC, since it utilizes a computer, not only the hardware but also the software of the system become complicated. For this reason, it is difficult to prepare a program or modify a sequence for a mechanical engineer or a field engineer not skilled in software. For the purpose of obviating the difficulty caused by using system words, although a system utilizing macro-instruction sets which are exclusively used for sequence controls has been proposed, prior art macro-instruction sets are interpreters so that there are such problems that the execution speed of the sequence is low and that the performance is limited.